Dr. Keith Erlandson, currently a senior technical swine veterinarian with Zoetis, worked from 2015 to 2020 directing a team of veterinarians for CP Group China. Starting in August 2018, nearly all the farms in China went into full lockdown, some for nearly six months.

Despite those efforts, however, by April 2019 the ASF had spread throughout the entire country, and pig-dense provinces were completely devastated. Shandong Province, previously one of the top five provinces in China for pig production, no longer has a pig industry to speak of.

It’s since come to light that the original report in August 2018 may not have been the original case, as there had been tissues testing positive going all the way back to March of that year. There’s a concern that the same thing could happen in the U.S., where infection makes its way into an area that’s not pig-dense, and veterinarians aren’t as familiar with pig diseases and can’t detect it early.

These insights from Dr. Erlandson should prove helpful, especially considering the new ASF cases detected in the Western Hemisphere just weeks ago.

How does ASF present and progress?

One of the most common misconceptions is that ASF presents in obvious and apparent ways. That’s not necessarily the case, as clinical signs aren’t always completely obvious at first.

Generally speaking, a farm with a thousand pigs will see a 3% mortality rate, around 30 pigs. In that case, the local vet will often assume that those pigs have porcine reproductive and respiratory syndrome (PRRS), prescribe based on their protocol, and follow up in a week or so.

But in many cases, what’s diagnosed as PRRS at first is actually ASF. The biggest clinical sign is vomiting, preceded by going off-feed. Dr. Erlandson and his team found that if those pigs refuse to get up one day, in two days they’ll be dead. So once animals start showing clinical signs, the decline happens rapidly.

Another thing to keep in mind is that ASF is a hemorrhagic disease. Once the pigs start to become ill, they have very erythematous purple-red ears, and their noses especially would become very red from the hemorrhages. As they get worse, they start to hemorrhage from the mouth, nose and anus. Post-mortem, there’s significant hemorrhaging from everywhere, including the cirrhosis surfaces, especially the small intestines, and even some under the skin. The lymph nodes, especially, are very large and hemorrhagic.

Experiencing the ASF outbreak in real-time

Dr. Erlandson and his team’s first encounter with ASF was in late August 2018. He was working at a 2,400-head sow farm and integrated around that farm were seven finishers, all within a 10-km radius. Those finishers produced around 60,000 pigs per year. Most notably, this farm was only 7 km from the very first case of ASF in Yunnan province. The farm was near the city of Shandong, which itself was near the smaller town of Shinde.

Just three days after the announcement of the first ASF case, the farm was completely locked down. People came by and disinfected the road in front of the farm at least three times a day, every day, as well as all the walkways and roads within the farm. The only thing that came into the farm was feed for the animals and food for the workers.

At the end of August, they found four boars to be off-feed. The next day, two of those boars had died, and three sows were off-feed the next day.

From the diagnosis, pigs located near where the original case was found were depopulated. For the next couple of days, all seemed quiet. But then, around 10 days later, there were some more dead pigs, and more sows off-feed. As mid-September approached, a clear pattern emerged. More pigs were going off-feed and dying within two days.

The problem was: since the outbreak was so new, every level of government in China was trying to get a handle on what was going on. Testing capacity was overwhelmed, and at that time they could only send samples to government labs. Around that mid-September mark, it was pretty obvious that the sows had ASF. By then, the farm made the decision to depopulate.

Generally, ASF takes a while to get started, but once it gets going, it goes very quickly. After the first clinical signs had appeared, it took 13 days for Dr. Erlandson and his team to realize what was really going on.

How to deal with ASF as an endemic disease

They came to realize pretty quickly that diagnosing the disease then completely depopulating wasn’t a sustainable way of dealing with it. After about six months, it became clear that ASF was now endemic, and producers are just going to have to learn to live with it.

Dr. Erlandson gave an example of a farm in southern China. If there were any dead sows or dead gilts, they would collect a sample from that animal, either blood or a swab from the thoracic cavity. However, they would hold those samples for up to a week before sending them to a lab. So there was one sample where the precise sampling date was unclear.

Turns out, that animal came out of a row in the breeding barn that was part of a group that was due to farrow. By the time that animal was tested and confirmed and had died, the other animals in that group had already been moved into the farrowing barn. This meant that, now, they had to test not only the sows but also environmental samples in the farrowing barn. Then they washed and disinfected everything, and thought they had gotten rid of of the virus.

But less than three weeks later, there was another set of positive samples on the other end of the barn, which then had to be depopulated. Then, after a month of negative testing, the farm was declared free of ASF. In all, that required a culling of 400 out of the 2,400 sows on the farm. They’ve been ASF-free ever since.

Granted, losing 400 animals is a big hit to a farm, but it’s small compared to losing the whole farm overall. Once that farm was ASF-free, they continued to do testing and removal procedures. In 70% of the cases, if they were able to find the ASF virus early enough, they had about a 70% chance of saving the farm. The other 30% usually happens when the virus was detected too late, and there’s just no way to save the farm.

Producers now have to rethink their processes and, like Dr. Erlandson and his team, develop the capabilities to test in their own laboratories. Most importantly, it’s important to realize that when there’s an ASF outbreak, culling animals is a necessity.

New biosecurity measures due to ASF

Dr. Erlandson also described the biosecurity measures that are now becoming commonplace to protect against ASF.

Workers who arrive at the farm shower into the living area, spend the night, then shower into the actual farm. They would go into an off-site containment area where you take a shower, put on site-specific clothes, have your hands and shoes swabbed for ASF and stay overnight. Once those tests come back negative, you go into a second isolation area, and do the same thing. In some cases, workers may end up spending two nights there. Once cleared, then they can actually go to the farm and shower in the living area, where they’ll spend another night then can go into the farm the next day. From the time you arrive until you can actually go into a barn and see a pig is around three to four days.

In terms of trucks, there are usually at least two or three truck washes, and most of them will have the capability of baking a trailer dry as well. So consider a feed truck, which starts at the feed mill, then goes into a truck wash where it’s washed, disinfected, and baked dry. Then it goes to a second washer where the same thing happens again.

Then the truck will go to the finishing farm and deliver the feed, but it won’t actually enter the farm site. It will either dump the feed into a central bin or, if that’s not feasible, into a separate feed truck that never leaves the site.

When the time comes to sell the pigs, there are dedicated internal trailers that will transport them to a slaughter transfer station, where they’ll be loaded into an external truck that takes them to the slaughter plant. Once that first truck is finished, it will be washed and disinfected; as will the second one, before it’s allowed to return to the farm.

This presents a significant capital investment, because not only do you need two trucks, but you also need the additional labor to load the pigs twice.

Yet even with all of these biosecurity measures, there are still cases that breakthrough on the farms. These could be caused by insects, rodents, aerial spread, feed or some other cause. Just in June, northern China lost 25-50% of their sows, even with these extreme measures, he said.